Question
Write a method called negativeSum that accepts a Scanner reading input from a file containing a series of integers, and print a message to the console indicating whether the sum starting from the first number is ever negative.
You should also return true if a negative sum can be reached and false if not. For example, suppose the file contains the following text:
38 4 19 -27 -15 -3 4 19 38
Your method would consider the sum of just one number (38), the first two numbers (38 + 4), the first three numbers (38 +4 +19), and so on to the end. None of these sums is negative, so the method would produce the following output and return false:
no negative sum
If the file instead contains the following numbers:
14 7 -10 9 -18 -10 17 42 98
The method finds that a negative sum of 8 is reached after adding the first six numbers. It should output the
following to the console and return true:
sum of -8 after 6 steps
Answer
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class NegativeSum {
public boolean negativeSum() throws FileNotFoundException {
// reads the input from Integers.txt file
File file = new File("${basepath}//Integers.txt");
try (// send file as an argument to the Scanner constructor
Scanner input = new Scanner(file)) {
int sum = 0;
int steps = 0;
while(input.hasNext()) {
sum += input.nextInt();
steps++;
if(sum < 0) {
System.out.println(sum + " after " + steps + " steps");
return true;
}
}
}
System.out.println("no negative sum");
return false;
}
// below method throws FileNotFoundException
public static void main(String[] args) throws FileNotFoundException {
NegativeSum ns = new NegativeSum();
System.out.println(ns.negativeSum());
}
}
Integers.txt file contains
25 -23 31 -32 12 -87 24 65 47 -23 19 -35 -1
Output:
-74 after 6 steps
true